FLUID-STRUCTURE IN SUPERCRITICAL XENON BY NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY AND SMALL-ANGLE X-RAY-SCATTERING

Chemical shifts for Xe-129 at 25 degrees C are presented for densities between 5 x 10(-3) and 2.2 x 10(-2) mol/cm(3), corresponding to press ures between 50 and 1000 bar. Also presented art small angle X-ray sca ttering results for xenon at 28 and 45 degrees C and pressures between 30 and 400 bar. The scattering results reveal the expected increase i n aggregation and correlation length near the critical density. The ch emical shifts exhibit deviations from the second-order virial equation over a broad range of densities. These deviations are also evident in calculations from integral equation theory. A departure from the cage model of solvent nearest neighbors due to repulsive solvation effects is discussed as a possible source of these deviations.